Download Genetics Notes

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How did the
study of
Genetics
begin?
Clip
Gregor Mendel
Genetics is the branch
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of biology that deals
with heredity. A great
deal of what we know
about genetics began
with the work of a
monk named Gregor
Mendel, who
experimented with
sweet pea plants in the
1800s.
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Mendel’s Work
• Mendel studied
the patterns of
inheritance in
pea plants.
• He chose seven
traits to follow.
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• Mendel needed to
make sure he had
plants that always
gave the same
offspring-called true
breeding.
• He “self-pollinated”
plants until he got
seeds that always gave
the same offspring.
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Some plants can self-pollinate or
cross-pollinate with another plant.
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 He took a purple
flower plant and
crossed it with a
white flower
plant?
 He called these
the parent
generation (P
generation)
 What do you
think the
offspring looked
like?
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Pollen
X
F1
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POLLEN
F2
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Mendel concluded:
2. Something is being passed from
parent to offspring. He called these
“Factors”
3. Sometimes you can see “it” and
sometimes you can’t see “it”.
4. If you can see it- it is dominant.
1. If it’s there and you can’t see itit’s recessive.
5. There are two versions of these
“FACTORS”.
6. To show the two version we use a
capital letter for the dominant (S)
version of the trait and a lower
case for the recessive version (s)
of the trait.
ADD TO NOTES: Each Version is
called an Allele.
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Each chromosome has many genes, but
the alleles may be different
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Alleles are different versions of the same gene.
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Common Physical Human TraitsDifferent Alleles
Trait
Dominant
Recessive
Chin cleft
Absent (C)
Present (c)
Dimples
Present (D)
Absent (d)
Free (F)
Attached (f)
Almond (A)
Round (a)
Straight (S)
Upward slant
(s)
Eyebrow
position
Connected (Y)
Not connected
(y)
Eyebrow
shape
Bushy (B)
Fine (b)
Long (L)
Short (l)
Round (R)
Square (r)
Present (P)
Absent (p)
Curly (H)
Straight (h)
Tongue rolling
Can roll (T)
Can't roll (t)
Widow's peak
Present (W)
Absent (w)
Earlobe shape
Eye shape
Eye position
Eyelash length
Face shape
Freckles
Hair
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Activity
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We have two
copies of all
of our
chromosomes
Why?
These are
called
Homologous
Chromosomes
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BOY OR GIRL?
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Karyotype
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DNA codes for Proteins
What is a gene?
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• A segment on the chromosome that codes
for a protein.
• People have two copies of each gene, one
copy inherited from the mother and the
other copy inherited from the father.
• There are many versions of each genealleles
Remember:
Genes come in pairs.
**One from your mother
**One from your father.
If the two alleles in
the pair are
identical, then the
condition called
homozygous. The
term “purebred”
is sometimes
used.
20.1
•
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If the 2 alleles are
different, the
condition is called
heterozygous.
The term “hybrid” is
sometimes used to
refer to
heterozygous.
What the genes/alleles
are …RR.…Rr
What the
organism looks
like……
Red…..White
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Genotype
Phenotype
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How did you
end up with
the traits
and genes
that you
got?
During
meiosis, each
egg or sperm
only gets one
copy of each
chromosome.
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Meiosis
Review
Animation
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Law of Dominance
Mendel’s
Laws
• States that the
dominant allele
will prevent the
recessive allele
from being
expressed.
•The recessive allele will appear when
it is paired with another recessive
allele in the offspring.
•Remember: Genes Come in Pairs!
Law of Segregation
(separation) states that
gene pairs separate
when gametes (sex
cells) are formed
•Each gamete has only
one allele of each
gene pair. (haploid)
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gene pairs separate
Goes
through
Meiosis
Mendel’s
Laws
A a
b B
S Phase
AA
aa
bb
BB
Makes
a copy
A
A
a
a
b
b
B
B
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Law of
Independent
Assortment
states that
different
pairs of
genes
separate
independently
of each
other when
gametes are
formed.
Mendel’s
Laws
Example:
Just because you get the gene for
brown hair does not mean you will
get the gene for blue eyes.
Animation
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REVIEW
1. A trait is a characteristic an individual
receives from its parents.
2. Genes carry the instructions responsible for
the expression of traits.
3. A pair of inherited genes controls a trait.
4. One member of the pair comes from each
parent.
5. Alternative versions of genes are known as
alleles.
REVIEW
Mendel’s Principles of Inheritance
•
Inherited traits are transmitted by genes which occur in
alternate forms called alleles
1. Principle of Dominance - when 2 forms of the same gene
are present the dominant allele is expressed
2. Principle of Segregation - in meiosis two alleles separate
so that each gamete receives only one form of the gene
3. Principle of Independent Assortment - each trait is
inherited independent of other traits (chance)
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Peas in a pod- Genetics Clip
Example EOCT Question:
Earlobe shape is a human trait. Some people have
free earlobes while others have attached
earlobes. Two parents with free earlobes have
four children. Three children have free earlobes
and one child has attached earlobes. If these
parents have another child, what is the
probability that the child will have attached
earlobes?
A 25%
B 50%
C 75%
D 100%
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Predicting possible
outcomes of a genetic
cross.
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Punnett Squares
• Geneticist use punnett squares to
determine the probability of a
combination of alleles.
• For example: If a heterozygous
black rabbit is crossed with a
heterozygous black rabbit, what
are the chances the offspring will
be black?
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B=Black
b= Brown
Genotypes?
Phenotypes?
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Claymation Clip
Example EOCT question:
In humans, a widow’s peak is dominant over
a continuous hairline. Mary’s father has a
widow’s peak, but Mary and her mother
have a continuous hairline. What is the
genotype of Mary’s father?
A HH
B Hh
C hh
D cannot be determined
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Incomplete Dominance
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Codominance
With codominance, a cross
between organisms with two
different phenotypes produces
offspring with a third phenotype
in which both of the parental
traits appear together.
DO NOT blend together.
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Codominance
• Both phenotypes
are expressed at
the same time.
• Example: Blood
Types
Genotype
IOIO
Phenotype
Type O
IAIO
IAIA
I BI O
I BI B
Type A
Type A
Type B
Type B
IAIB
Type AB
There are 3 alleles
for blood typemultiple alleles
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Codominance
R = allele for red flowers
W = allele for white flowers
red x white ---> red & white spotted
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Polygenic traits
Many traits are
controlled by
more than one
gene.
Ex: Skin Color
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Sex Linked Traits
Traits associated with particular
sexes are called sex-linked or
X-linked traits.
Examples of
Sex-linked
Traits:
•Red-green
colorblindness
•Hemophilia
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Linked Genes
• Occurs when particular alleles are inherited
jointly.
• They tend to be inherited together, for
example, red hair and freckles.
1st 22 are Autosomes, the last pair
(XY) are sex chromosomes)
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Charts that show relationships
within a family
Pedigree
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•
•
•
•
•
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How many boys? __________________
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How many Girls? __________________
3
How many generations? _______________
4
How many with the disorder? ____________
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How many marriages are shown? ____________
1.
How many
generations?
2. How many
carriers?
3. How many
affected
males?
4. How many
affected
females?
5. Autosomal or
sex-linked?
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Autosomal-Dominant
What can you tell by the pedigree?
Dominant or recessive?
Autosomal or sex-linked?
SEX-LINKED
What can you tell by the pedigree?
Dominant or recessive?
Autosomal or sex-linked?
SEX-LINKED
What can you tell by the pedigree?
Dominant or recessive?
Autosomal or sex-linked?
Autosomal
Dominant or recessive?
-Dominant
Autosomal or sex-linked?
NO
carriers
when
Dominant.
Autosomal
-Recessive
Carriers
when
recessive.
• Pedigree Practice-Smart board
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Huntington’s Disease
• Progressive,
degenerative disease
that causes certain
nerve cells in your brain
to waste away.
• Experience uncontrolled
movements, emotional
disturbances and mental
deterioration.
• No cure. Fatal. ages:3060
• Dominant Allele
49 1/2
Colorblindness
• Sex-linked trait
• Gene for color vision
located on the X
chromosomes.
• Males are more likely
to have
colorblindness
because they have
only one X
chromosome
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What do
you see?
The individual with normal color vision will see a 5
revealed in the dot pattern. An individual with
Red/Green (the most common) color blindness will
see
a
2
revealed
in
the
dots.
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Down Syndrome
• 3 copies of chromosome #21.
• Sister chromatid DO
NOT separate
during Meiosis.
• (or homologues fail to separate )
• Nondisjunction
• Also called:
Trisomy 21
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Nondisjunction
• Sister chromatid DO NOT separate during
Meiosis.
• Or homologues fail to separate during Meiosis.
Down Syndrome - Trisomy 21
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Nondisjunction
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Cystic Fibrosis
• CF is caused by a
recessive allele on
chromosome #7.
• More than 1,000
different mutations in
the CFTR gene have
been identified
• Deletion of 3 bases.
• Affects the body's
respiratory and
digestive systems.
59.1
Cystic Fibrosis
• 1 in 29 Caucasian Americans
have the allele.
– Asian & African-less likely to have.
– More than 10 million Americans carry the
cystic fibrosis gene
• Treatments:
– Pancreatic enzyme replacement
therapy to allow proper food
digestion
– Bronchodilators (also used by
people with asthma) that help keep
the airways open
– Inhaled antibiotics to kill the
bacteria that cause lung infections
– Chest physical therapy, in which
the patient is repeatedly clapped
on the back to free up mucous in
the chest
Gene therapy ?????? Currently in clinical
trials
59.2
Hemophilia
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Sickle
Cell
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Mis-shaped
blood cells.
People who carry the tendency
to have sickle cell anemia are
less likely to die from malaria.
Sickle
Cell
•Most
commonly
affects
AfricanAmericans.
•About 1 out of
every 500
AfricanAmerican
babies born in
the United
States has
sickle cell
anemia.
Mis-shaped
blood cells.
Interesting
fact:
Unlike
normal red
blood cells,
which can
live for 120
days,
sickleshaped cells
live only 10
to 20 days.
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Tay-Sachs
• Progressively destroys nerve cells (neurons)
in the brain and spinal cord.
• Harmful quantities of a fatty acids
accumulate in the nerve cells of the brain.
• Caused by insufficient activity of an enzyme
called beta-hexosaminidase A that catalyzes
the biodegradation of acidic fatty materials
• More common in people of Ashkenazi
(eastern and central European) Jewish
heritage
• Fatal
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Gene Therapy
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Example EOCT question:
What is nondisjunction?
A. failure of chromosomes to separate
during meiosis
B. failure of the cytoplasm to divide
properly
C. the insertion of a gene into a different
chromosome
D. the deletion of a gene from a
chromosome
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Which of the following shows how
information is transformed to make a
protein?
A DNA RNA  protein
B gene  chromosome protein
C cell respiration  ATP  protein
D ATP  amino acid  protein
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Information on mRNA is used to make a
sequence of amino acids into a protein by
which of the following processes?
A replication
B translation
C transcription
D transference
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Pea plants have seeds
that are either round or
wrinkled. In this cross,
what will be the
phenotypic ratio of the
offspring?
A
B
C
D
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50% RR and 50% Rr
25% RR, 50% Rr, and 25% rr
50% round seeds and 50% wrinkled seeds
100% round seeds
What is a source of
genetic variation?
A mutation
B adaptation
C replication
D transcription
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In Mendel’s experiments with
a single trait, the trait that
disappeared in the first
generation
and reappeared in the next
generation is called the
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A homozygous trait
B dominant trait
C recessive trait
D heterozygous trait
•What
pattern
of
inherita
nce is
this?
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Human Genome Project
What
would one
gene say to
another?
Cloning